This invention relates to a trim tab actuator for a marine propulsion device and more particularly to an automatically activated trim tab device for maintaining a watercraft on its course.
As is well known, the propulsion device of a watercraft can, at times, generate a force on the watercraft which tends to cause it to deviate from its steered course. For example, in watercraft that are propelled by a propeller and particularly those using an outboard drive such as the outboard drive unit of an inboard-outboard drive or an outboard motor per se, the thrust of the propeller tends to cause the watercraft to turn. For example, if the propeller is rotating in a clockwise direction as viewed from the rear, the boat tends to veer to the left from its steered course. The faster the propeller rotates, the greater the force tending to cause such deviation. In order to avoid such course deviations, it has been the practice to provide some form of trim tab on the outboard drive unit across which the water will flow and which will tend to resist the turning force of the propeller. Obviously, a fixed trim tab will not provide the desired course stability under all running conditions of the watercraft.
It has also been proposed to employ trim tabs that are pivotal relative to the outboard drive and which tend to create hydrodynamic forces on the outboard drive. One such type of trim tab is employed to assist in the steering of the outboard drive. Of course, such arrangements are not advantageous in maintaining the watercraft in a steered course but only assist in course changes. Alternatively, there have been proposed mechanically actuated trim tabs which are intended to keep the watercraft on a steered course. However, when the trim tab is pivoted by a mechanical mechanism that is responsive only to a predetermined mechanically sensed condition, the desired results cannot be obtained satisfactorily.
It is, therefore, a principal object of this invention to provide an improved trim tab actuating device for a marine propulsion unit.
It is a further object of this invention to provide an automatically activated trim tab that will keep a watercraft on its course and regardless of the running conditions encountered.
It is a further object of this invention to provide an automatically operated trim tab that will keep a watercraft on its course in response to any of a variety of sensed varying running conditions.